Move blob from compiler/ to util/

There's nothing whatsoever compiler-specific about it other than that's
currently where it's used.

Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>

src/compiler/nir/nir_serialize.h

@@ -25,7 +25,7 @@
 #define _NIR_SERIALIZE_H
 
 #include "nir.h"
-#include "compiler/blob.h"
+#include "util/blob.h"
 
 #ifdef __cplusplus
 extern "C" {